Switch condition indicator



SWITCH CONDITION INDICATOR Filed Feb. 9, 1962 .3 FIG. I

OSC

INVENTOR.

WILLY BORBERG ATTORNEY.

United States Patent 3,175,047 SWITCH CONDITION INDICATOR Willy Borberg, Briarclilf Manor, N.Y., assignor to General Precision, Inc., a corporation of Delaware Filed Feb. 9, 1962, Ser. No. 172,228 2 Claims. (Cl. 179-82) This invention rel-ates to indicator-systems and in particular to systems for indicating the on condition of a switch.

One application of this invention is in the operation of drive-in motion picture theatres. In such theatres it is the practice to provide each patrons automobile with a speaker to supply the audio: portion of the talking motion picture presentation. In one car speaker system the speaker receives its audio signal inductively. This is done by circulating the audio signal currents in a cable laid on the ground beneath all of the cars, and by providing in each speaker set a pickup coil and audio amplifier. Power for the amplifier is supplied by a small dry battery in the speaker set. The patron turns the dry battery on when he uses the set and is supposed to turn it oil at the end of the performance.

In practice, the patron often forgets or simply neglects to turn off the speaker set battery power supply. Upon leaving the grounds he leaves the speaker set at the theatre oflice, where the attendant stacks and stores the speaker sets in preparation for the next show.

It has been found that a considerable proportion of speaker sets are turned in with the battery switch left on. Although the attendant may check for this and turn many of the switches oil, some escape him, with the result that some of the sets are stored with the switch on. The battery is rapidly exhausted, so that the next patron to receive the set either has a weak amplifier or no audio signal at all. The augmented battery replacement has been found to constitute a serious expense.

The present invention provides simple additional circuitry to make it unlikely that a set will be stored with the battery switch on. The circuitry includes a second contact arm on the amplifier battery switch, and provides a pickup device and a neon signal lamp. Power to operate the neon signal lamp is transmitted at a suitable frequency without wires from a generator in the vicinity, either by electromagnetic radiation or by induction. This power, for example, may be at kcps. although any other frequency, either higher or lower, may be employed. The power is picked up by the pickup device and generates a voltage across its terminals. If the battery switch of the speaker set has been left on, this voltage lights the neon lamp. This serves as a signal to the attendant that the switch is on. When he turns the switch off, the neon lamp goes out.

One purpose of this invention is to provide a lamp indicator for a switch to indicate the switch condition.

Another purpose is to provide a test accessory for use with drive-in theatre induction speaker sets to prevent the likelihood of storing some speaker sets with the battery switch left on.

A further understanding of this invent-ion may be secured from the detailed description and drawings, in which:

FIGURE 1 is a schematic wiring diagram of the circuit of the invention.

FIGURE 2 is a view of the speaker set.

Referring now to FIGURE 1, a speaker 11 is actuated by amplified audio currents from an amplifier 12. The amplifier input is controlled in volume by a manually operated volume-control potentiometer 13 which is energized from an audio induction pickup coil 14. The coil is positioned within the plastic housing of the speaker, which is shown in perspective in FIGURE 2. The ampli- 3,175,047 Patented Mar. 23, 1965 "ice fier power supply consists of a battery 16, FIGURE 1, one side of which is connected through the contact arm 17 of a manually-operated switch 18 to the amplifier 12 and the other side of which is connected to a common return connection 19.

The circuit as so far described constitutes a conventional induction-operated speaker set. In operation, the speaker set is hung on the sill of an automobile door by the hook 21, FIGURE 2, with the speaker grille 22 facing inside the car. The switch 18, generally apart of the volume control as indicated by the dashed line 23, FIG- URE 1, is turned on and the volume control knob 24 is turned to bring the sound volume up as desired. The audio pickup coil 14 picks up the audio signals, usually from a cable laid on the ground near the car, and sound issues from the speaker.

To the foregoing conventional elements there are added, for the purposes of this invention, a high frequency pickup coil 25 and a small neon lamp 27. The high frequency pickup coil 26 is preferably tuned to the high frequency generator frequency by means of a shunt capacitor or by its internal distributed capacitance. Such distributed capacitance is indicated by the dotted capacitor 28. However, the Q or efiiciency of the coil 26 and its resonant circuit should be fairly low so as not to be sharply tuned to the high frequency generator frequency, obviating necessity for close frequency control, and so as not to be susceptible to operation by strong radio station transmitter fields. The coil 26 may consist of an air core coil transversing the periphery of one side inside the speaker set plastic cabinet.

The coil 26 and lamp 27 are connected in series. The other coil terminal is connected to the common conductor 19 and the other lamp terminal is connected to a contact 29 of the switch 18. The associated contact arm 31 is connected to contact arm 17.

A 20 kc. induction field is provided by an oscillator 32 operating at this frequency and having a transmitting coil 33. The transmitting coil 33 is preferably tuned approximately to the transmitting frequency, either by a separate capacitor or by distributed capacitance, and may consist of wire wound around the entire periphery of one or two walls of the room where the speaker sets are stored when not in use. The dashed arrows 34 indicate that the induction field of the coil 33 floods the entire speaker storage area.

During normal operation the speaker set hangs on the window sill of the car and provides the audio part of the motion picture performance for the occupants of the car. The audio field is picked up by induction by the coil 14 but the potential induced across it is far less than the 60 volts or more required to light the neon lamp 27. Moreover, the lamp 27 and coil 26 are shunted by the low impedance battery 16, so that the lamp 27 re mains unlit and constitutes an open circuit. in its branch. The audio currents from coil 14 will flow principally in the common conductor 19 instead of through the battery 16. The coil 26 will pick up only negligible amounts of the audio signal, the frequencies in which are below 7500 c.p.s. Thus, in normal use, the addition of the coil 26, lamp 27 and switch contact 29 has no effect on operation and cannot cause any battery drain.

After the motion picture performance the cars drive out past the speaker set storage building and the speaker set is collected from each car by the attendant. The attendant either stacks the speaker sets one on top of the other or hangs them on hooks on one or more of the interior walls of the speaker set storage building. When the collection has been completed the sets have normally all been stored with the face of each facing outward and exposed. The attendant then turns on the 35 oscillator 32, FIGURE 1. The neon lamp 27 will light the magnitude of the energy induced in said audio in any set in which its switch 18 is closed, and the atinduction coil being insufficient to operate said inditendant, seeing at a glance Whichsets have closed switches, cator, and opens the switches. This both opens the battery, elimisaid high frequency pickup coil having a frequency nating drain, and extinguishes the lamp. 5 characteristic such that only negligible amounts of What is claimed is: audio frequency signals are induced therein. 1. A motion picture theatre speaker system for use in 2. A motion picture theatre speaker system as set an automobile comprising, forth in claim 1 wherein said indicator consists of a neon an audio induction pickup coil adapted to be exposed lamp having a striking potential well in excess of the to an audio frequency induction field, 10 potential of said source of battery potential and the magan amplifier having its input connected to said audio nitude of any audio signal energy imposed thereon.

induction pickup coil, a source of battery potential for said amplifier, said References Cited y the Examine! vbattery potential energizing said amplifier through a UN T D S A PA first switch contact, 15 a high frequency pickup coil and an indicator confoivnsend nected across said source of battery potential in se- 0 m ries with a second switch contact operated in unison FOREIGN PATENTS with said first switch contact, 226,427 4 /58 Australia.

tmeans for generating a high frequency induction field 20 815,288 6/59 Great Britain.

of a frequency and amplitude sufiicient to operate said indicator when said switch contacts are closed, NEIL C. READ, Primary Examiner. 

1. A MOTION PICTURE THEATRE SPEAKER SYSTEM FOR USE IN AN AUTOMOBILE COMPRISING, AN AUDIO INDUCTION PICKUP COIL ADAPTED TO BE EXPOSED TO AN AUDIO FREQUENCY INDUCTION FIELD, AN AMPLIFIER HAVING ITS INPUT CONNECTED TO SAID AUDIO INDUCTION PICKUP COIL, A SOURCE OF BATTERY POTENTIAL FOR SAID AMPLIFIER, SAID BATTERY POTENTIAL ENERGIZING SAID AMPLIFIER THROUGH A FIRST SWITCH CONTACT, A HIGH FREQUENCY PICKUP COIL AND AN INDICATOR CONNECTED ACROSS SAID SOURCE OF BATTERY POTENTIAL IN SERIES WITH A SECOND CONTACT OPERATED IN UNISON WITH SAID FIRST SWITCH CONTACT, MEANS FOR GENERATING A HIGH FREQUENCY INDUCTION FIELD OF A FREQUENCY AND AMPLITUDE SUFFICIENT TO OPERATE SAID INDICATOR WHEN SAID SWITCH CONTACTS ARE CLOSED, THE MAGNITUDE OF THE ENERGY INDUCED IN SAID AUDIO INDUCTION COIL BEING INSUFFICIENT TO OPERATE SAID INDICATOR, AND SAID HIGH FREQUENCY PICKUP COIL HAVING A FREQUENCY CHARACTERISITC SUCH THAT ONLY NEGLIGIBLE AMOUNTS OF AUDIO FREQUENCY SIGNALS ARE INDUCED THEREIN. 